## Objects Obscured by Earth’s Curvature and Zoom Factor

From an observer on a shore, the distance to the horizon is 5 km (3 miles), or more if the observer is higher. Therefore, Earth’s curvature obscures objects starting from that distance. If the objects are not large enough, we need an optical aid, like zooming in using a camera, to see them in the first place.

Flat-Earthers often show us wide-angle photos to demonstrate that objects are not obscured by Earth’s curvature. In reality, in such photos, objects far enough to be obscured by Earth’s curvature cannot be resolved. It is hard to see objects obscured by Earth’s curvature if the objects themselves are not visible in the picture.

## Camera Entrance Pupil Size and the Zoom Factor

The entrance pupil is the opening in front of a camera that allows light to enter. If it is partially obscured, light can still come through the unobscured part, and the camera can still see the object.

In one of those “experiments,” flat-Earthers placed an obstacle in front of a camera, very close to the lens, so that an object is partially visible. At the widest angle setting, the person appears partially visible. But it turned out that zooming in will fully reveal the person. Flat-Earthers claim it is how objects can vanish behind the horizon if Earth is flat and how they can reappear by zooming in. In reality, zooming enlarges the camera’s entrance pupil, letting the camera to see over the obstacle.

## Zooming in on a Partially Obscured Ship

Zooming in makes the camera’s field of view narrower, and in effect, it magnifies the center portion of the image. Zooming in using the optical zoom can improve angular resolution, but will never reveal a distant object that is obscured by another object.

Flat-Earthers claim that zooming in will fully reveal a ship that is partially obscured. In reality, the proportion of the ship which is hidden compared to that which is visible stays the same in the entire zoom range.